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Category: Super-Tech

Using Carbon-NanoTube (CNT) sheets that we can make now, we might push towards ~2,200 km/s. Of course there will be structural mass and the payload reducing the top speed – thus we might hit ~1,800 km/s tops with CNT sheets, if made perfectly reflective. Even for lower reflectivity the speed will be about ~1000-1500 km/s.

How hard can we push it? A 1999 study by Dean Spieth, Robert Zubrin & Cindy Christensen for NASA’s Institute of Advanced Concepts (NIAC), which can be found here, examined using CNTs arranged in a spaced-out grid. One of the curiosities of optical theory is that, for a given range of wavelengths, the reflective material doesn’t have to be an unbroken sheet – it can be an open-grid.

Computing the reflectivity of such things is difficult – best to make it and measure it – but estimates of how a CNT grid would perform suggests that a CNT sail might accelerate at ~18 m/s2 at 1 AU from the Sun, implying a final speed of 2,320 km/s. Dropping inwards and launching from 0.019 AU would mean a final speed of 16,835 km/s (0.056c), allowing a probe to reach Alpha Centauri in just 78 years, propelled by sunlight alone!

To send people, rather than rugged robots, a different approach will be needed – to be discussed in Part 3.

Carbon is the material of the Future. Graphite, graphene, bucky-balls and nanotubes all have amazing properties. And then there’s diamond – which seems to come in several varieties, albeit rare and/or theoretical.

Making enough of any of the allotropes – different carbon forms – is rather tricky, aside from raw graphite, which can be mined. Diamonds fortunately can be made fairly easily these days – very pure diamond crystals can be (almost) made as large as one likes. Thus Jewel Diamonds, the kind De Beers sets the standard for, have to be slightly impure crystals, as they’re thus provably natural.

Carbon nanotubes are proving easier to make and to make into useful forms. One application caught my eye:

…which have the rather amazing property of being strong and yet massing just ~27 milligrams per square metre. If we can dope it (add a sprinkling of other elements) to make it more reflective, then it makes rather impressive solar-sail material. Sunlight’s pressure – as felt by a reflective surface facing flat to the Sun – is about 1/650 th of the sun’s gravity, so creating lift against the Sun’s gravity requires very large, light sheets. And doped CNT sheets – if 100% reflective – would experience a lift factor (ratio of light-pressure to the sail’s own weight) of 57 (!)

In theory that means a suitably steered solar-sail made of CNT sheet could send itself away from Earth’s orbit and reach a final speed of 42*sqrt(57-1) km/s ~ 315 km/s. If it swooped past Jupiter then swung in hard for the Sun, scooting past at 0.019 AU, then it would recede at ~2,200 km/s.

Kim Stanley Robinson’s latest book “2312” is set in that titular year in a Solar System alive with busy humans and thousands of artificial habitats carved from asteroids. Earth is a crowded mess, home to eleven billion humans, but no longer the home of thousands of species, now only preserved, flourishing in fact, in the habitats. Spacers, those living in space, are long-lived, thanks to being artificially made “bisexual” (male & female) and some are living even longer by virtue of small size. Humans live from the Vulcanoids – a belt of asteroids just 0.1 AU from the Sun – out to Pluto, where a quartet of starships are being built for a 1,000 year flight to GJ 581. Mars has been terraformed, via Paul Birch’s process of burning an atmosphere out of the crust to make canals, while Venus is snowing carbon dioxide (another Birch idea.) The larger moons of Jupiter and Saturn are extensively inhabited and debating their terraforming options.

On Mercury Stan introduces us to the moving city Terminator, which runs along rails powered entirely via thermal expansion of the rails as they conduct heat from Mercurian day and radiate it away in the Mercurian night. Mercury is a planet of art museums and installations of art carved out of the periodically broiled and frozen landscape. Sunwalkers walk forever away from the Sunrise, braving the occasional glimpse of the naked Sun, which can kill with an unpredictable x-ray blast from a solar flare.

The two main protagonists are Swan, an Androgyn resident of Mercury, a renowed designer of space-habitats whose mother, Alex, has just died; and Wahram, a Wombman resident of Titan, who is negotiating access to solar energy for the terraforming of his home world. Due to a freak “accident” the two must journey through the emergency tunnels underneath Mercury’s Day-side, an experience which draws them together inspite of being literally worlds apart in personality and home-planets.

There’s a lot going on in 2312 and Stan only shows us a slivver. Plots to reshape the worlds and plots to overthroe the hegemony of humankind. But for our two interplanetary lovers such forces can’t keep them apart.

Of course, I’m not here to review the book. This being Crowlspace, I’m looking at the technicalities. Minor points of fact have a way of annoying me when they’re wrong. For example, Stan mentions Venus wanting to import nitrogen from Titan, which is rather ridiculous. The atmosphere of Venus is 3.5% nitrogen by volume, which works out as the equivalent of 2.25 bars partial pressure. Or about 3 times what’s on Earth. So importing nitrogen would be the equivalent of the Inuit importing ice.

Stan is critical of interstellar travel being portrayed as “easy” in Science-fiction. He mentions a fleet of habitats being sent out on a 1,000 year voyage to a star 20 light-years away – given the uncertainties of these things and the size of habitats, that’s not an unreasonable cruise speed. Yet he describes it as being “a truly fantastic speed for a human craft.” But at one point he mentions that a trip to Pluto from Venus takes 3 weeks, an unremarkable trip seemingly, yet that requires a top-speed of 0.022c – significantly higher than the starships!

He’s a bit vague about the pace of travel in the Solar System via “Aldrin cycles” – cycling orbits between destinations, timed to repeat. Buzz Aldrin developed the concept for easy transport to Mars – have a space-station with all the life-support in the right orbit and you only have to fly the passengers to the station, rather than all their supplies. The station either recycles everything or is resupplied by much slower automated freighters using electric propulsion. Stan’s mobile habitats do the former, with some small topping-up. But such Cyclers are slow. Stan mentions a Mercury-Vesta Cycler trip taking 8 days. Not possible for any Cycler orbit that’s bound to the Sun (i.e. cycling) – a straight-line parabolic orbit would take a minimum of 88.8 days. A proper Cycler needs to be on an orbit that can be shaped via the gravity of the planets to return it to the planets it is linking together, else too much fuel will be expended to reshape the orbit. Preferably an orbit that isn’t too elliptical else the shuttle fuel bill is too high. A minimum-energy Hohmann orbit would take 285 days to link Mercury and Vesta.

These are quibbling points. The real meat of the book is the optimistic future – a dazzlingly diverse one – that is basically plausible. Enticingly possible, in fact. Yet the optimism is tempered by the fact that not everyone is living in a wise, open society. Earth, even in 2312, remains a home to suffering masses, their plight made worse by the greenhouse effect’s flooding of low-lying parts of the Globe, and the Sixth Great Extinction’s erasure of most large animals from the planet (fortunately kept alive or genetically revived in the mobile habitats.) New York is mostly flooded, becoming a city of canal-streets, something I can imagine New Yorkers adapting to with aplomb.

The real challenge of the 24th Century, in Stan’s view, is the terraforming of the Earth, remaking a biosphere that we’ve ruined in our rush to industrialise. Perhaps. We certainly have many challenges ahead over the next 300 years…

If our Universe is open, either flat or hyperbolic in geometry, then it will expand forever… or at least until space-time’s warranty expires and a new vacuum is born from some quantum flip. Prior to that, most likely immensely distant, event the regular stars will go out and different sources of energy will be needed by Life in the Universe. A possible source is from the annihilation of dark matter, which might be its own anti-particle, thus self-annihilating when it collides. One possibility is that neutrinos will turn out to be dark matter and at a sufficiently low neutrino temperature, neutrinos will add energy to the electrons of atoms of iron and nickel by their annihilation. This is the energy source theorised by Robin Spivey (A Biotic Cosmos Demystified) to allow ice-covered Ocean Planets to remain hospitable for 10 billion trillion (1023) years.

Presently planets are relatively rare, just a few per star. In about 10 trillion years, or so, according to Spivey’s research, Type Ia supernova will scatter into space sufficient heavy elements to make about ~0.5 million Ocean Planets per supernova, eventually quite efficiently converting most of the baryon matter of the Galaxies into Ocean Planets. A typical Ocean Planet will mass about 5×1024 kg, be 12,200 km in diameter with 100 km deep Ocean, capped in ice, but heated by ~0.1 W/m2 of neutrino annihilation energy, for a planet total of ~50 trillion watts. Enough for an efficient ecosystem to live comfortably – our own biosphere traps a tiny 0.1% of the sunlight falling upon it, by comparison. In the Milky Way alone some 3,000 trillion (3×1015) Ocean Planets will ultimately be available for colonization. Such a cornucopia of worlds will be unavailable for trillions of years. The patience of would-be Galactic Colonists is incomprehensible to a young, barely evolved species like ours.

James Lovelock once estimated Earth’s biosphere would crash in about 100 million years when carbon dioxide levels dropped too low. James Kasting and Ken Caldeira updated the model to include a different photosynthetic cycle amongst land plants, pushing back Doomsday to about 900 million years in the Future. Those “900 million years” before Earth overheats is based on a certain model of Earth’s response to the Sun’s gradual rise in luminosity. That particular model assumes everything else will remain the same, but that’s unlikely. If the partial pressure of nitrogen declines, then the greenhouse effect from carbon dioxide will decline and the Earth could remain habitable to life for another 2.3 billion years. Alternatively because the greenhouse instability of the Earth is driven largely by the thermal response of the oceans, if Earth became a desert planet then it would remain habitable until the Sun reaches ~1.7 times its present output. Combined with a reduced atmospheric pressure, it means Earth might remain habitable until the end of the Sun’s Main Sequence in 5.5 billion years.

But this all assumes no technological intervention. Several scenarios are possible – a variably reflective shell engulfing the Earth is the simplest. Planet moving and Solar engineering are more dramatic possibilities. Given sufficient thrust a leisurely spiral of the Earth outwards from the Sun would compensate for the brightening, though the pace of travel would need to be rather rapid for a 6 billion trillion ton planet to escape the more dramatic stages of the Sun’s Red Giant Branch (RGB).

Once the Sun hits the Horizontal Branch/Helium Main Sequence, the habitable zone will be roughly where Jupiter will be – as the Sun’s mass loss during the RGB will cause all the orbits to expand by ~30%. The HB offers just 110 million years of stability before the Sun begins a series of dying spasms known as the Asymptotic Giant Branch. Not healthy for any of the planets. If the RGB’s mass-loss can be tweaked a bit, then the Sun won’t hit the HB at all and will slowly decline into being a helium white dwarf. Earth can remain in the white dwarf Sun’s habitable zone then for billions more years, more if it spirals inwards as it cools.

As a fan I can tell you it was an SF-Fan’s dream come true to meet, in the flesh, so many SF-writers and so many Icarii, as well as the Heart & Mind of the TZF. People I met, for the first time, but have corresponded with for a while…

Others I met/heard who maybe aren’t so well-known, but may prove influential in times to come. Such as Young K. Bae, laser propulsion research and inventor of the Photonic Thruster (a very clever multi-bounce photon-propulsion system.) Mark Edwards, of Green Independence, who might have a way of feeding Starship Crews and the whole of Starship Earth.

Fast thoughts – David Nyeland gave a us BIG hint on how to launch a Starship in 100 years… reach out to EVERYONE.

Too much to tell on the very aggressive schedule here, so a detailed report will need to wait, but I met a FAN! You know who you are. Thanks for the encouragement and I promise more content – I have some actual journal paper ideas gestating and I will need input from my audience, I suspect. One is a paper on Virga-style mega-habitats and Dysonian SETI, to use a new idea from Milan Cirkovic. The other looks at exoplanets and Earth-like versus the astrobiology term of “habitable” – the two are not the same and the consequences are sobering. The recent paper by Traub (go look on the arXiv) which estimates 1/3 of FGK stars has a terrestrial planet in the habitable zone does NOT mean there’s Earths everywhere. What it does mean and how HZ can be improved as a concept is what I want to discuss.

More later. I have my talk to review and get straight in my head – no hand notes, though I have practiced it – plus I want something helpful to say to Gerald Nordley, mass-beam Guru, on the paper he graciously added me as a co-author. Also I will summarize my talk and direct interested readers to the new web-site from John Hunt, MD, on the interstellar ESCAPE plan.

The Falcon 9 launch vehicle was developed from a blank sheet to first launch in four and half years for just over $300 million. The Falcon 9 is an EELV class vehicle that generates roughly one million pounds of thrust (four times the maximum thrust of a Boeing 747) and carries more payload to orbit than a Delta IV Medium.

The Dragon spacecraft was developed from a blank sheet to the first demonstration flight in just over four years for about $300 million. Last year, SpaceX became the first private company, in partnership with NASA, to successfully orbit and recover a spacecraft. The spacecraft and the Falcon 9 rocket that carried it were designed, manufactured and launched by American workers for an American company. The Falcon 9/Dragon system, with the addition of a launch escape system, seats and upgraded life support, can carry seven astronauts to orbit, more than double the capacity of the Russian Soyuz, but at less than a third of the price per seat.

Note the cost of developing the “Dragon” which is the first private aerospace vehicle proven capable of return from orbit. About $300 million, with a dry mass of about ~4.2 tons, thus ~$72 million/ton to develop. To develop large Mars mission vehicles might be assumed to cost similar amounts per ton of aerospace machinery. But can it be done even cheaper?

The SpaceX’s Falcon-9 Heavy rocket will have a launch capacity of 53 metric tons to low Earth orbit. This means that if a conventional hydrogen-oxygen chemical rocket upper stage were added, it would have the capability of sending 17.5 tons on a trajectory to Mars, placing 14 tons in Mars orbit, or landing 11 tons on the Martian surface.

The company has also developed and is in the process of demonstrating a crew capsule, known as the Dragon, which has a mass of about eight tons. While its current intended mission is to ferry up to seven astronauts to the International Space Station, the Dragon’s heat shield system is capable of withstanding re-entry from interplanetary trajectories, not just from Earth orbit. It’s rather small for an interplanetary spaceship, but it is designed for multiyear life, and it should be spacious enough for a crew of two astronauts who have the right stuff.

Thus a Mars mission could be accomplished utilizing three Falcon-9 Heavy launches. One would deliver to Mars orbit an unmanned Dragon capsule with a kerosene/oxygen chemical rocket stage of sufficient power to drive it back to Earth. This is the Earth Return Vehicle.

A second launch will deliver to the Martian surface an 11-ton payload consisting of a two-ton Mars Ascent Vehicle employing a single methane/oxygen rocket propulsion stage, a small automated chemical reactor system, three tons of surface exploration gear, and a 10-kilowatt power supply, which could be either nuclear or solar.

The Mars Ascent Vehicle would carry 2.6 tons of methane in its propellant tanks, but not the nine tons of liquid oxygen required to burn it. Instead, the oxygen could be made over a 500-day period by using the chemical reactor to break down the carbon dioxide that composes 95% of the Martian atmosphere.

Using technology to generate oxygen rather than transporting it saves a great deal of mass. It also provides copious power and unlimited oxygen to the crew once they arrive.

Once these elements are in place, the third launch would occur, which would send a Dragon capsule with a crew of two astronauts on a direct trajectory to Mars. The capsule would carry 2500 kilograms of consumables—sufficient, if water and oxygen recycling systems are employed, to support the two-person crew for up to three years. Given the available payload capacity, a light ground vehicle and several hundred kilograms of science instruments could be taken along as well.

The crew would reach Mars in six months and land their Dragon capsule near the Mars Ascent Vehicle. They would spend the next year and a half exploring.

Using their ground vehicle for mobility and the Dragon as their home and laboratory, they could search the Martian surface for fossil evidence of past life that may have existed in the past when the Red Planet featured standing bodies of liquid water. They also could set up drilling rigs to bring up samples of subsurface water, within which native microbial life may yet persist to this day. If they find either, it will prove that life is not unique to the Earth, answering a question that thinking men and women have wondered upon for millennia.

At the end of their 18-month surface stay, the crew would transfer to the Mars Ascent Vehicle, take off, and rendezvous with the Earth Return Vehicle in orbit. This craft would then take them on a six-month flight back to Earth, whereupon it would enter the atmosphere and splash down to an ocean landing.

Spending ~2.5 years in a Dragon capsule will take a couple of claustrophiles, but people have endured in remarkably nasty conditions. So why not? It’s daring, but is it necessary?

Zubrin asks for a cryogenic upper-stage to throw the Mars vehicles to Mars, but is that really needed? Can better performance be achieved by using a slightly different approach? In a previous post I outlined the Falcon Heavy Tanker (FHT) – essentially a Falcon Heavy Stage 2 with a stretched tank and a docking collar for coupling to a Dragon. I estimated 55 tonnes of RP-1/LOX could be placed in orbit and a FHT dry-mass of 2.5 tonnes. To get to Mars takes ~3.7 km/s from LEO, the so-called Trans-Mars Insertion (TMI) delta-vee, thus with a vacuum Isp = 342s, that means the Falcon Heavy Tanker can push 27.2 tonnes into a TMI orbit, thus a net payload of ~24.7 tonnes. With aerobraking that’s considerably more than the Mars Society’s quoted payloads, providing somewhat better living conditions for the explorers.

Of course the payloads need to be orbitted separate to the FHTs, but at less than half the Falcon Heavy’s usual 53 tonne payload, that means 2 separate Mars payloads can be orbitted by one vehicle, and supported by a separately orbitted crew in a Dragon. Potentially we can reduce the FHTs to just three to support a beefier Mars Semi-Direct mission which doesn’t mean living in a Dragon capsule for 2.5 years! Alternatively we launch the Mars Ascent Vehicle directly via a single Falcon Heavy, as per the Mars Society plan, and launch the Mars-bound Habitat and Earth Return Vehicles via 2 FHT launches and 1 Falcon Heavy. Four Falcon Heavy launches versus 3, but delivering more payload.

Zubrin is, I suspect, hoping to minimize the cost of developing new systems, thus using two Dragons and only needing to develop a low-mass Mars Ascent Vehicle. However the current Dragon probably can’t be used as a Habitat for +2 years with some development work, thus the difference between the two approaches is probably negligible. I appreciate his gumption and burning desire to get a finger-hold on Mars as soon as possible, but I’d like to see the developed systems able to do more than a stunt.

…Carr & Coley pose the idea that some black holes get through a cosmological Bounce (a Crunchy Big Bounce) relatively unscathed. George Zebrowski used something like that idea in his “Macrolife” novel (1979), in which Intelligent life from previous Big Crunchy Bounces survived in the Cosmic Ergosphere. Poul Anderson did it earlier in “Tau Zero” (1970), but the problem with both is that the mass of the Universe, even if it has a net spin, probably won’t form a black-hole style ergosphere when it contracts inside its own event horizon. The topology is all wrong for regular cosmology and it’s doubtful whether a white-hole style cosmos expanding in a precosmic void would ever go Big Crunch. However they might’ve been partly right, thanks to this intriguing preprint…

…in which Vyacheslav I. Dokuchaev speculates that Life might orbit within supermassive black hole event horizons because it can and it might use the emissions of the Cauchy Horizon and massive time dilation for technological purposes. If Life can live inside a Black Hole, and Black Holes can survive the Crunchy Big Bounce, then might not Life survive too? Or am I speculating over a data-void on too many planks of inference? Perhaps only a dive into a Black Hole will ever tell us for sure, though whether we can ever send the news home is debatable. According to Igor Novikov we might be able to access the regions inside via a wormhole specifically dropped in…

…which might provide a means to reach the aliens inside from past Cosmic Cycles. Perhaps that’s exactly what they want or are hoping for. Of course such vastly old entities – if they’ve survived – might be so utterly foreign to us cosmic youths that we might be unwittingly unleashing “Elder Gods” of Lovecraftian style moral indifference. Or perhaps we’d find them to be akin because of the daring that sent them across the Event Horizon in the first place? Cosmic Extreme Sports, anyone?